This invention relates to a method for reducing dot gain with respect to the operation of a multi-level halftoning color-image output device. More specifically, it relates to such a method which is based upon the output-device-specific creation of a pixel infeed intensity correction curve which is employed for adjusting pixel infeed intensity with regard to the feeding of a pixel into a selected multi-level halftone image output device. More particularly, the term “pixel infeed” as used herein specifically refers to the feeding in to such an output device of a colored pixel for ultimate outputting by that device. For the purposes of illustration herein, a preferred manner of practicing the present invention is described in a context where the image output device is a CMYK, multi-level, halftone printer.
It is typical for dot gain to become a problem in, for example, an imaging, or printing, system wherein an output color image is delivered as a halftoned image. Generally speaking, and as is well understood by those skilled in the art, such so-called dot gain typically has two different aspects, one of which is referred to as physical dot gain and the other of which is referred to as optical dot gain.
The present invention proposes a unique methodology for reducing, significantly, both categories of dot gain, in a device-specific manner, and with respect to an output device, such as a printer, which is capable of outputting, in a multi-level manner, a halftoned color image.
According to the invention, for each output color in a halftone mode which an image output device is capable of delivering, a special dot-gain intensity correction curve is generated to control, effectively, the infeed intensity (infeed to the output device) of each pixel in a halftoned, device-infeed pixel data stream. The mentioned pixel infeed intensity correction curve proposed by the present invention is prepared, with respect to a specific color-image output device, by causing that device, in what can be thought of as a calibrating mode, to output, for each of its operative colors, selected halftone dot patterns which are then individually examined for the purpose of determining what kind of a multi-level pixel infeed intensity control needs to be applied to cause an output color image which is halftoned to appear substantially without any appreciable dot gain problems. How this device-specific calibrating activity takes place is described in detail below.
Use of the resulting intensity correction curves has been found to offer a very effective solution to the mentioned halftone output dot-gain issue.
The various important features and advantages of the invention will now become more fully apparent as the description which follows is read in conjunction with the accompanying drawings.